A 301 "Permanent Redirect" is a common method for redirecting from one URL to another.
The number 301 refers to the HTTP Status code value found in the HTTP response header that is sent by the web server in order to let the client know that the requested resource has moved permanently, and can be found at a new location.
In contrast to a 302 temporary redirect, this is typically the redirection method you'll want to use on your site for SEO purposes. That's because a 301 permanent redirect typically passes all the link juice from the first URL to the target URL. Therefore, when a page moves, it's possible to keep the same ranking position, thus preserving your SEO efforts. It's also a signal to search engines that the original URL is no longer used, so they will usually remove it from their index.